The present invention relates to electronic circuitry, and more particularly, but not exclusively, relates to relational logic for a content addressable memory.
Content addressable memory (CAM) is used in many different applications, such as redundant xe2x80x9cback-upxe2x80x9d memory systems for Application Specific Integrated Circuits (ASICs), associative caches, and databases. In common use, an input is compared to each CAM memory location and any matches are identified. Some systems have incorporated schemes to provide relational information as an alternative or addition to match status. Unfortunately these schemes typically involve the addition of a significant amount of circuitry and/or processing time. Accordingly, there is a demand for further advancements relating to CAM technology. The present invention satisfies this demand and has other benefits and advantages.
One embodiment of the present invention is a unique content addressable memory system. Other embodiments include unique devices and methods involving relational operations for a content addressable memory.
In a further embodiment, a Content Addressable Memory (CAM) device includes unique logic to provide an indication corresponding to an inequality between an input and one or more locations. The inequality corresponds to a greater-than, greater-than-or-equal-to, less-than, or less-than-or equal-to relational operation.
Another form of the present application includes a number of content addressable memory cells and a number of relational logic circuits. The circuits each compare a stored bit of one of the cells to a respective bit of an input word. The relational logic circuits each include a selection operator to route a first signal input to a respective output if the stored bit and respective bit are equal and to route a second signal representative of a relational inequality between the word and data stored in the cells to the output if the stored bit and the respective bit are unequal.
In another embodiment of the present invention, an apparatus includes a number of content addressable memory cells and a number of relational logic circuits each corresponding to a different one of the cells. Each one of these circuits is coupled to another by a corresponding one of a number of relational signal pathways, and each include a device with an input coupled to one of these pathways and an output coupled to another of these pathways to selectively pass a signal from the input to the output in response to a control signal.
Yet another embodiment comprises operating a content addressable memory that includes a multibit storage location, first relational logic corresponding to a most significant bit of the location, and second relational logic corresponding to a next most significant bit of the location. A multibit input to the memory is provided and a first signal is selected for output with the first relational logic if a first bit of the input and the most significant bit of the location are different. A second signal is selected for output with the first relational logic if the first bit of the input and the most significant bit of the location are equal. This second signal is received from the second relational logic.
Accordingly, one object of the present invention is to provide a unique content addressable memory.
Another object is to provide a unique system, method, or apparatus directed to relational operation of a content addressable memory.